The Adjacent Possible


Confronted with a changing world, organisms can move, adjust, adapt, or die


In physical space -> move


In physiological / behavioral space -> adjust


In genetic / adaptive space -> adapt


If no adjacent possible -> die


Responses are not mutually exclusive

The Adjacent Possible for other species


If environmental conditions are changing…



  • What are the adjacent possible options for survival?


  • What determines the adjacent possible?
    • Organismal traits
    • Environmental features
    • Dynamics of change


  • Can a trait adjust?

Organismal responses to change: Adjust


  • Adjust: non-genetic shifts in organismal traits in different environments
    • phenotypic plasticity


  • Adjust response happens at the individual level and within a single generation
    • What does this mean?

Organismal responses to change: Adjust



Genotype: inherited genetic information


Phenotype: observable traits or characteristics



What is the connection between genotype & phenotype?


Genotype x Environment = Phenotype variation?


G x E interactions are the foundation of phenotypic plasiticity

What is phenotypic plasticity?



When a single genotype can produce multiple phenotypes depending on environmental conditions




  • Inducible defenses are classic example
    • animals and plants
    • oftern fast
    • stabilize population dynamics
    • dedicated sensory systems to interpret the environment


Daphnia produce horns and neck teeth in presense of predators

Density-induced grasshopper plasticity


Some shore crabs shift colors diurnally!






Camouflage


Thermoregulation


Signaling


UV light protection

What is phenotypic plasticity?



When a single genotype can produce multiple phenotypes depending on environmental conditions




  • Plasticity doesn’t have to be for morphological traits.


  • Physiological, developmental and behavioral traits can also exhibit plasticity


  • Behavior has long been considered the ‘most plastic’ phenotypic trait
    • quickest response to temporal changes

What is phenotypic plasticity?



When a single genotype can produce multiple phenotypes depending on environmental conditions




  • Developmental plasticity: the ability of an individual to modify its development in response to environmental conditions
    • might facilitate the evolution of novel traits


  • How developmental flexibility promotes innovations that persist over evolutionary time is unclear


  • However, exposure to environmental variation is a characteristic feature of normal development

Are all traits plastic?




  • Optimal responses to environmental challenges would include perfect plasticity
    • organism possesses perfect information on its current environment
    • mechanisms to produce an appropriate phenotypic response at all points in development


  • Instead, traits exist on a spectrum that are determined exclusively by genetics and those influenced mostly by the environment
    • no organisms is entirely or infinitely plastic


  • Interesting point: Organisms in heterogeneous (variable) environments are more likely to have selection of traits that can be plastic
    • low genetic diversity can limit selection of plastic traits

How do you test for phenotypic plasticity?



How do you figure out if a trait is controlled by genes, the environment or both?

How do you test for phenotypic plasticity?



Effect of genotype only (not phenotypically plastic under these conditions)

How do you test for phenotypic plasticity?



Effect of environment only (YES phenotypically plastic under these conditions)

How do you test for phenotypic plasticity?



Effect of both environment and genotype (genotype by environment interaction)

Are global change and the adjust response compatible?